@react-email/ui@6.0.0

### Major Changes

* 3ca799d: Rename @react-email/preview-server -> @react-email/ui.

  Same exact code, but with a different name. The equivalent `react-email` version has also been udpated accordingly. The old @react-email/preview-server will be deprecated.

  ### How to migrate

  **Update your dependencies** -- remove `@react-email/preview-server`, install `@react-email/ui`:

  ```diff
  - npm install @react-email/preview-server
  + npm install @react-email/ui
  ```

### Patch Changes

* 5bd0d43: copy toolbar insights for AI
* 91ca688: remove extra margin from sending button